1. Field of the Invention
The present invention relates to materials for effective shielding against non-ionizing and ionizing radiation, such as electromagnetic effects, interference, or neutrons, and, more particularly to lightweight, flexible materials with sufficiently high conductivity and magnetic properties for effective electromagnetic effects shielding.
2. Description of Related Art
To prevent damage from non-ionizing and ionizing radiation, such as electromagnetic effects, interference, or neutron electromagnetic effects (EME) such as lightning strike damage and electromagnetic interference on composite aircraft vehicles, highly conductive materials are required to protect the interior electronics, cockpits, and passenger cabins. Metallic materials such as metal layer coatings or metal meshes are often used to shield the airframes effectively from the EMEs, however, weight reduction may not be maintained with these heavy metal structures and the nature of open mesh structure may not protect some localized lightning attachment effectively. On the other hand, lightweight polymeric materials with conventional conductive inclusions may not provide sufficient conductivity required for shielding EMEs without sacrificing the mechanical properties. Metallization or metal coating can be applied directly to the inclusions such as nanotubes (NT), prior to forming the composite. However, thorough dispersion of the heavy metallized nanotubes in a polymer resin is a big challenge to accomplish.
The prior art discloses no known lightweight polymeric composite materials for achieving sufficient shielding effects against EMEs for aerospace or electronic applications. Prior work generally utilized heavy metal layers or meshes by covering the entire airframe. Metallic foams, conductive polymers, and conventional polymer composites with conductive inclusions have been employed to protect airframes from EMEs as well, but the required level of shielding effect was not achieved.
Metallic layers or coatings may provide effective shielding capabilities; however, high weight penalties of using metallic materials limit their applications. Metallic foams do not provide robust mechanical integrity to use as structural applications and the level of the conductivity may not be sufficient for the EME shielding. The conductive polymers tend to lose their conductivity at elevated temperatures (>100° C.) by dedoping or dehydration. Conventional polymer composites require very high conducting filler loadings to reach the level of conductivity for EME shielding, which often inevitably lead to reductions in strength and toughness as well as weight penalties.
Future aerospace vehicles require structural airframe materials with tailorable properties to manage the weight, temperature, structural, radiation, and electromagnetic challenges associated with high-speed, high-altitude flights. Although a number of lightweight materials such as nanostructured polymers, aerogel, honeycomb, metallic foam, and lattice block have been proposed to reduce weight of aerospace vehicles, lack of thermal stability and mechanical durability primarily limits their use for airframe structure and propulsion systems. Adding non-metallic lightweight materials in the airframe structure for weight reduction may cause new challenges such as a series of electromagnetic effects (EME) (lightning strike, Electromagnetic interference) and high altitude radiations. Therefore, highly conductive and multifunctional lightweight composite materials are required to protect aerospace vehicles from various EME and radiations. Currently, no materials can achieve this level of conductivity and functionality to protect the vehicles from EME and radiations.
The essential concept in this work is to develop novel Metallized Nanotube Polymer Composites (MNPC), which are composed of lightweight polymer matrix, superstrong nanotubes, and functional nanoparticle inclusions.
An object of the present invention is to provide lightweight, flexible materials with sufficiently high conductivity and magnetic properties for effective EME shielding.
An object of the present invention is to provide impregnated metal preferentially deposited on the nanotube surfaces inside of the composite, which can improve the conductivity of the nanotube networks.
An object of the present invention is to provide an environmentally benign process, requiring no toxic chemical solvents or reducing agents for incorporating metal particles in this invention and leaving no residual solvents behind.
An object of the present invention is to provide a method for producing lightweight EME shielding which is economically beneficial by recycling CO2 fluid on a large scale.
Finally, it is an object of the present invention to accomplish the foregoing objectives in a simple and cost effective manner.